From experiments using colitis model mice, the present inventors discovered that siRNAs that suppress the CHST15 gene expression have a therapeutic effect against Crohn's disease or ulcerative colitis. Specifically, the present inventors discovered that the siRNAs which suppress the CHST15 gene expression can serve as an agent for promoting mucosal healing, in particular, an agent for treating Crohn's disease or ulcerative colitis, and thereby completed the present invention.
